Good Practices

A Unique Combination of Trenchless TechnologiesMicrotunnellingProject “Dondukov Blvd.”

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Microtunnelling

 

Microtunnelling was implemented for the first time in Bulgaria by companies-members of BATT.

Stroitelna Mehanizatsia AD, Kazanlak and Raicommerce AD, Sofia, in collaboration with the German company HERRENKNECHT applied microtunnelling method for the construction of sewerage in the area of Mertostation 8 /in the area of Sofia University St. Kliment Ohridski/ during the spring of 2006.

In the course of the construction works of Metrostation 8 it turns out that the path of the rail-way should pass under an existing sewerage. The location of the site – one of the busiest cross roads in Sofia, as well as the existing of complex underground infrastructure, convinced the main contractor of the project, Taisei Corporation to definitely reject the conventional sewerage construction method and to search for a solution in application of trenchless technology, in the face of Stroitelna Mehanizatsia AD and Raicommerce Construction. 

The great project depth /from 7 to 12 meters/, the complicated soil conditions, namely succession of clay, sand and combination of both, as well as the high level of underground waters, definitely excluded the most widely applied method in Bulgaria namely Horizontal Directional Drilling. The existing difficulties united the specialists from Stroitelna Mehanizatsia and Raicommerce Construction and together they made a decision of using of the new in Bulgaria microtunneling trenchless method. The consortium which was founded especially for this project took the important task. The colleagues from Herrenknecht were asked for assistance and they also supplied the microtunnelling machinery – model AVN 600 XC. During the process of work the Bulgarian team was supported by an experienced operator from Herrenknecht. 

170 m. of DN 600 sewer glass-ceramic pipes, divided in 4 sections were installed. The pipes which were used are the most suitable for great depths, they sustain ground load pressure and have 100 years guarantee, but practically they are ever lasting. With this technology, project inclinations from 1.3 î/îî to 1.45 î/îî were achieved. The team reached an average speed of 5 m. per day.